the digestive system by tushar
TRANSCRIPT
DIGESTION
The chemical breakdown of complex biological molecules into their component parts.
Lipids to fatty acids
Proteins to individual amino acids
Carbohydrates into simple sugars
DIGESTION
Chemical Changes the chemical composition of food with the aid of digestive
enzymes
Carbohydrate Protein Lipid
Digestive enzymes are special proteins that help break up large molecules of food into very tiny molecules that can be absorbed and used by the cells in the form of nutrition.
FUNCTION
Produces various chemicals to break down the food.
Filters out harmful substances.
Gets rid of solid wastes.
THE DIGESTIVE TRACT
A long muscular tube with many sections and areas.
Begins with the mouth and ends with the anus.
THE DIGESTIVE TRACT Parts of the Digestive Tract
Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Anus
ACCESSORY PARTS
Organs that are not in the digestive tract but helps in the digestion
Teeth Tongue Salivary glands Liver Gall bladder Pancreas
MOUTH
Functions: Food enters in the mouth or
oral cavity Tasting Mechanical breakdown of food Secretion of salivary glands
(salivary amylase)
MOUTH Structures in the mouth that aids digestion:
Teeth – cut, tear, crush and grind food. Salivary glands – produce and secrete
saliva into the oral cavity. Parotid (beneath the cheeks) Submaxillary (below the jaw bone) Sublingual (below the tongue)
– saliva moistens the food and contains enzymes (ptyalin or salivary amylase) that begins digestion of starch into smaller polysaccharides.
MOUTH Tongue
Mixes and rolls food into tiny mashed up bits (Bolus)
Pushes the bolus toward the pharynx and into the esophagus when swallowing.
MECHANISM OF SWALLOWING
Swallowing is a coordinated activity of the tongue, soft palate, pharynx and esophagus.
Phases
Food is pushed into the pharynx by the tongue. (voluntary)
Tongue blocks the mouth
Soft palate closes off the nose
Larynx (Adam’s Apple) rises so the Epiglottis (a flap of tissue) can close the opening of the trachea.
ESOPHAGUS A straight muscular tube that is about 10 inches (25
cm) long which connects the mouth with the stomach
Food takes about 4 to 8 seconds as it passes through to the stomach.
Its walls contain smooth muscles that contracts in wavy motion .
Cardiac Sphincter (ring-like valve) relaxes to allow food into the stomach.
STOMACH J-shaped muscular sac
Has inner folds (rugae) that increases the surface area of the stomach.
Churns and grinds together the bolus into smaller pieces.
Food is mixed with gastric juices (hydrochloric acid and enzymes) secreted by the stomach walls.
HCL helps break down food and kills bacteria that came along with the food.
STOMACH
Pepsin – major enzyme; converts proteins into peptides in the presence of HCL.
Mucus – lubricates food and protects the gastric lining from strong digestive juices.
Converts the bolus into a liquid (chyme) after 4 hrs of mechanical and chemical digestion
Chyme passes through the pyloric sphincter into the small intestine.
ACCESSORY ORGANS
Produce or store enzymes that helps in digestion.
Liver
Largest gland of the body Stores vitamins A,D,E,K Stores sugar and glycogen Produces bile (watery, greenish substance) Secretes bile to the gall bladder via the
hepatic duct and cystic duct.
ACCESSORY ORGANS
Gall bladder
Stores bile in between meals Secretes bile to the duodenum through
the bile duct during mealtime. Bile contains bile salts, pigments,
cholesterol and phospholipids. Bile is an emulsifier NOT an enzyme. Emulsifier – dissolves fat into the
watery contents of the intestine.
ACCESSORY ORGANS
Pancreas Produces a juice that contains
enzymes (amylase and insulin) to break down carbohydrates, fats and protein.
Secretes the juice into the duodenum through the pancreatic duct.
SMALL INTESTINE
Long (20 ft), coiled tube beneath the stomach.
Has three parts:
Duodenum – upper part; about 10 in; connected to the stomach.
– where the digestive juices from the pancreas and the liver combine with chyme making it thin and watery.
Jejunum – about 8 ft
Ileum – about 12 ft
SMALL INTESTINE
Takes about 4 – 8 hrs to complete its journey.
Mucosa (inner wall) – secretes several enzymes that acts on the food.
Where the pancreatic enzymes are emptied into.
Digested nutrients are absorbed through intestinal walls.
Absorbed materials cross the mucosa into the blood then other parts of the body for storage or further chemical change.
SMALL INTESTINE
Has folded inner walls covered with fingerlike projections (villi; sing. – villus)
Each villus has tinier projections called microvilli that absorbs digested food.
Villi and microvilli increases the surface area of the small intestine for greater absorption.
Peristalsis moves the undigested food to the large intestine.
MOVEMENT IN SMALL INTESTINE:
Mixing: Segmental contraction that occurs in small intestine
Secretion: Lubricate, liquefy, digest
Digestion: Mechanical and chemical
Absorption: Movement from tract into circulation or lymph
Elimination: Waste products removed from body
LARGE INTESTINE
A.k.a. Colon larger diameter, but shorter (5 ft) Water is absorbed from the undigested
food making the waste harder until it becomes solid.
Waste stays for 10 – 12 hours.
LARGE INTESTINE
Waste is pushed into the expanded portion (rectum) of the large intestine.
Solid waste stays in the rectum until it is excreted through the anus as feces.
Appendix hangs on the right side of the large intestine.